Andrew Young, a major ally of President Carter's bid for a second term, has warned that U.S. shifts toward hard-line policies in the Caribbean and northern Africa could cause great disillusionment among American blacks and other groups whose support is crucial to Carter's candidacy.

In an interview last week, the former United Nations ambassador stressed that he supports his old boss and will actively use his considerable influence with black voters to help Carter in his contest against Sen. Edward M. Kennedy (D-Mass.) for the Democratic presidential nomination.

But Young also warned, "I'm going to fight to ensure that the foreign policy direction I helped to set when I was in the administration is maintained." He made clear that, in the three months since he left the U.N. post amid a storm of controversy, some of the administration's actions have struck him as "wrong and cause for concern."

In particular, Young singled out two issues for criticism -- the attempt to respond to discovery of a Soviet combat brigade in Cuba with a display of Cold War rhetoric and muscle flexing, and the decision to provide weapons to help Morocco's autocratic King Hassan fight guerrillas in the western Sahara.

He challenged both stances as "not helpful to overall U.S. interests" and said there is a danger that they will be seen by those groups that helped to elect Carter in 1976 -- "the blacks and other minority groups, the young, the clergy, the liberal intellectuals" -- as a backing away from the administration's commitment to human rights and to dealing with the Third World on terms divorced from the eastwest rivalries of the superpowers.

"I'm not saying that's happening," Young stressed. "I think the administation's commitment to what's right is solid. But when you get close to an election, there's a tendency to try to play both sides -- to appease the hawks by putting on a big show of anti-communist saber-rattling about things that aren't really serious security issues.

"So," he continued, "I can understand if the president thinks it's going to help win the Florida primary by beating up on Fidel Castro and Cuban-Soviet menace in the Caribbean. When I was in the civil rights movement, we used to say there was a distinction between preaching and policy.

"Right now, while I might be a little upset about some of the preaching, I'm not worried about the policy," he said. But he added pointedly: "If the policy starts following the preaching too closely, I might get very upset."

The warning implicit in Young's words was especially significant because of the unique position he occupies in the U.S. political spectrum.

To many people in the generation whose political outlook was shaped by the ferment of the Vietnam war, Young, with his outspoken advocacy of human rights and sympathy for the aspirations of the Third World, became the foremost symbol of what they saw as a resurgent, post-Vietnam idealism in American foreign policy.

In the black community, these factors, coupled with his role as the first black to have an important voice in the foreign policy process, made him a hero of almost mythic proportions.

That was demonstrated with explosive force last summer when Young was forced to resign the U.N. ambassadorship for violating official policy by meeting with a representative of the Palestine Liberation Organization. The result was a roar of anguished protest from the black community, a rush by many other black leaders to show solidarity with Young by embracing the PLO and, for a time, the threat of a deep split between American blacks and Jews over U.S. Middle East policy.

Whether Young can transform his standing among blacks and liberals who share his policy views into votes for Carter is still an open question. But, in the interview, he made clear that his purpose was to articulate the foreign policy concerns of these constituencies and to underscore their importance in next year's political battles.

"Sure, the major issues, especially for blacks, are going to be things like jobs and inflation and the economy," he said. "But don't underestimate the impact that foreign policy can have on the activist, liberal wing of the Democratic Party.

"Look back to 1976 when black votes were decisive in electing Jimmy Carter," he argued. "Back then, all the Democratic candidates were saying pretty much the same things on domestic issues.If anything, Carter probably was the most conservative of them all.

"Yet one of the things that helped to get him the overwhelming black vote was that he spoke out clearly about southern Africa and the treatment of blacks there. The black community heard that and decided that his position on civil rights in southern Africa was an indicator that he would by sympathetic to the aspirations of blacks and women and other minorities here at home."

Turning to specific issues, Young cited the Caribbean as an area "where we're suffering some great losses because we've let the fuss over Soviet troops in Cuba make us lose sight of the real problem and look at things with a Cold War view."

"That simply does not apply," he insisted, "not even in Cuba. The way we're attacking Cuba is like shooting a cannon at a rat. It's nonsense for us to be so obsessed with Cuba and Fidel Castro. He's a nuisance, and that's how we should treat him -- as a nuisance.

"Instead, we've built Castro up into a bogeyman," Young asserted. "We've taken a guy on a small island and made him into a major international figure, instead of reducing him to proper size by ignoring him. We keep driving him further into the Soviet orbit, instead of showing the flexibility that might make him more independent. o

It doesn't help us in the Third World; it doesn't help us at home, except maybe in the Florida primary," he said, "and the people who want to run away with this policy are doing so to the peril of U.S. interests."

In addition, Young argued, the get-tough policy toward Cuba is having a polarizing effect in the Caribbean "because it's making us victims of insensitivity of the problems of other area leaders like Prime Minister Michael Manley of Jamaica and the people in some of the smaller islands like Grenada."

Their problems, he said, "are the problems of development and poverty. They're trying to manage countries that are close to unmanageable. They're under great pressures that include the need to appease their left wings. That means being friendly with Cuba and looking to Castro for some help."

"We shouldn't get upset when they speak to their own people's frustration and discontent by dealing with Cuba. We should be giving them a lot of understanding and support instead of taking Cold War postures that force them to make them-or-us choices."

Young made a similar point about the decision to sell arms to Morocco, which is engaged in a struggle in the western Sahara against Polisario Front guerrillas who want the area to be an independent Arab state. The guerrillas are backed by Algeria, and Young contended that the U.S. decision will only serve to polarize tensions in the region.

Without saying so directly, he implied that the decision resulted from the influence of Carter's national security affairs adviser, Zbigniew Brzezinski, and State Department Middle East experts seeking to appease Saudi Arabia, a backer of Hassan's conservative government.

These groups, Young said, take the "simplistic view that Algeria is a radical state with a bias toward the Soviets and Morocco is a conservative state on our side. The real truth is a lot more complicated."

"Algeria," he noted, "is our major trading partner in the area, one that does almost $4 billion worth of business with us a year. We're not going to do U.S. industry of U.S. interests any favors by alienating the Algerians.

"And," he added, we're not doing Morocco any favors by trying to create an illusion of strength with guns that won't even get there for two years. If King Hassan is in trouble, the threat comes not from the people in the western Sahara but from the unfulfilled aspirations of his own people, and he'd be far better served by $100 million spent on internal development than on guns.

"The way to solve the problem is not by shipping in guns," he said, "but by using our diplomacy with Hassan, with the Algerians, with the Saudis -- by trying to get them all to understand that what the region needs is not guns but stability and peaceful development."

It is especially important for the Carter administration to understand these things, Young said, because his rival, Kennedy, is a liberal who could take away much of Carter's support if the president moves too far right in his foreign policy.

"I'll be with Carter," he said, "but I also expect to be with the Democratic Party next November, and I'll be perfectly willing to support Ted Kennedy if he wins the nomination and if he remains true to his liberal principles.

"I'm concerned less with individuals than with issues," he said. "I want a candidate who can appeal to the hopes and ideals of our people and give the country a direction for the problems that will face us in the 1980s. I support Jimmy Carter because, even though I disagree with him about some things, I think he's smart enough and honest enough to do what's good for the country.

"If that changes, then I'll change," he said. "But I don't think it will. I can see where there are pressures to play to the right in foreign policy, but I don't think it really helps. Carter's natural battleground is to run on the values of those who elected him in 1976, and that's where I believe he'll be."